The present disclosure describes systems and techniques relating to image processing methods and apparatus, and more particularly, to methods and apparatus for demosaicking artifact suppression.
Digital cameras often acquire imagery using a single-chip CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) sensor whose surface is covered with a color filter array (CFA). The CFA consists of a set of spectrally selective filters that are arranged in an interleaving pattern so that each sensor pixel samples one of the three primary color values (for example, red, green and blue values). These sparsely sampled color values are referred to as CFA samples. To render a full-color image from the CFA samples, an image reconstruction process commonly referred to as CFA demosaicking is applied.
An immense number of demosaicking methods have been used in image processing pipelines. Many adaptive CFA demosaicking methods have been proposed to exploit the spectral and spatial correlations among neighboring pixels in order to have optimal reconstruction outputs. But even with the most advanced demosaicking methods, artifacts associated with this reconstruction process still arise. There are three basic types of demosaicking artifacts: (1) zipper artifacts refer to abrupt or unnatural changes of color differences between neighboring pixels, which manifest as an “on-off” pattern; (2) false color refers to noticeable color errors as compared to the original image, which occurs mostly around sharp edges; and (3) isolated dots refer to noticeable bright or dark spots, which occur in high spatial frequency areas with sharp edges.